This invention relates generally to reactors for processing semiconductor substrates, and more particularly, to exhaust systems for barrel epitaxial reactors.
A variety of reactors has been used to process semiconductor substrates. Some of these reactors have incorporated extraction systems to process gases exhausted from the reactors.
U.S. Pat. No. 4,556,584, entitled xe2x80x9cMethod For Providing Substantially Waste-Free Chemical Vapor Deposition of Thin-Film on Semiconductor Substrates,xe2x80x9d of Sarkozy issued on Dec. 3, 1985 disclosed a system that included a first comparatively low-efficiency thin-film deposition stage and a second comparatively high-efficiency effluent-waste stream removing stage for depositing substantially all of the effluent-waste stream produced by the deposition stage onto disposable baffles. As described by Sarkozy, the second stage was an ultraviolet enhanced vacuum chemical vapor deposition diffusion furnace.
U.S. Pat. No. 4,753,633, entitled xe2x80x9cMethod and System for Vapor Extraction From Gases,xe2x80x9d of Chiu issued on Apr. 5, 1988 disclosed a plasma extraction reactor for removing vapor phase waste from effluent gas streams. This patent simply uses a different type of reactor in the exhaust stream.
Yet another type of heated reaction chamber is disclosed in U.S. Pat. No. 5,417,934, entitled xe2x80x9cDry Exhaust Gas Conditioning,xe2x80x9d of Smith and Timms issued on May 23, 1995. In this apparatus, exhaust gases are exposed first to silicon, or a silicon-rich alloy or substance, and then exposed to calcium oxide or a calcium containing mixture. The apparatus was surrounded by a hollow cylindrical heater that incorporated an electrical resistance heater.
European Patent Application Publication No. EP 0 823 279 A2, entitled xe2x80x9cMethod and Apparatus for Treating Exhaust Gases From CVD, PECVD or Plasma Etch Reactorsxe2x80x9d taught yet another exhaust gas reactor configuration. Again, the exhaust gas reactor configuration included an electrically heated jacket.
U.S. Pat. No. 5,422,081, entitled xe2x80x9cTrap Device for Vapor Phase Reaction Apparatus,xe2x80x9d of Miyagi issued on Jun. 6, 1995 disclosed a trap that did not utilize a heater. Miyagi taught that for efficient removal a combination of small diameter discs (57 mm outer diameter and 52 mm inner diameter) and large diameter discs (119 mm outer diameter and 94 mm inner diameter) of stainless steel or aluminum. Miyagi taught that the spacing between the discs was critical in determining the collection efficiency.
Thus, these prior art disclosures show that while exhaust traps have been used, a given trap configuration is dependent both on the gases treated, the configuration of the trap, and characteristics of the particular reactor associated with the trap. Consequently, a particular trap design cannot be migrated to another reactor configuration. These prior art exhaust traps are intended to assist in the scrubbing of the exhaust gasses. The references are concerned. with the composition of the gas exiting from the trap and not particulate contamination in the processing reactor.
According to the principles of this invention, a novel exhaust particulate controller for receiving process gas from a substrate processing reactor has a housing with an inlet and an outlet. A liner is mounted within the housing. The liner has a first opening about the inlet and a second opening about the outlet. A plurality of baffles is mounted within the housing to form a plurality of chambers bounded by the liner and the plurality of baffles.
Each baffle includes a first surface bounding a first opening with a first dimension and a second surface bounding a second opening of a second dimension. The second dimension is smaller than the first dimension. An inner surface of the baffle extends from a boundary of the first opening to a boundary of the second opening to define a gas flow path through the baffle. Each baffle is positioned in the housing with the second surface closest to the outlet.
In one embodiment, the liner is selected from the group of liners consisting of a graphite liner, a silicon carbide liner, a silicon carbide coated graphite liner, a quartz liner, and a bead-blasted quartz liner. Similarly, the plurality of baffles is selected from the group of baffles consisting of graphite baffles, silicon carbide baffles, silicon carbide coated graphite baffles, quartz baffles, and bead-blasted quartz baffles.
The exhaust particulate controller has a longitudinal axis, and the gas flow path through a first baffle in the plurality of baffles is above the longitudinal axis, and the gas flow path through a second baffle located adjacent to, but separated from the first baffle is below the longitudinal axis.
The exhaust particulate controller of this invention may have any desired shape and in one embodiment, the controller has a cylindrical shape. The shape of the controller defines the shape of housing and consequently, the shape of the liner.
In another embodiment, the exhaust particulate controller for receiving process gas from a substrate processing reactor includes a cylindrical container having an inlet fixture extending from a closed end surface of the cylindrical container. The inlet fixture bounds an inlet opening. A first liner end element is mounted in an interior of the cylindrical container. The first liner end element is a cylinder with a closed end. The closed end bounds an opening substantially aligned with the inlet opening.
A first baffle is mounted in the interior of the cylindrical container adjacent the first liner end element. The first baffle includes a first surface bounding a first opening with a first dimension and a second surface bounding a second opening of a second dimension where the second dimension is smaller than the first dimension. An inner surface of the first baffle extends from a boundary of the first opening to a boundary of the second opening to define a gas flow path through the first baffle.
A liner spacer element is mounted in the interior of the cylindrical container adjacent the first baffle and then a second baffle is mounted in the interior of the cylindrical container adjacent the first liner spacer element so that the second baffle is adjacent to, but separated from the first baffle. Like the first baffle, the second baffle includes a first surface bounding a first opening with a first dimension and a second surface bounding a second opening of a second dimension where the second dimension is smaller than the first dimension. An inner surface of the second baffle extends from a boundary of the first opening to a boundary of the second opening to define a gas flow path through the second baffle.
A second liner end element is mounted in the interior of the cylindrical container after the second baffle. The second end element is a cylinder with a closed end that bounds an exhaust opening.
A cylindrical cover is removably attached to the cylindrical container. The cylindrical cover includes an outlet fixture extending from an end surface of the cylindrical cover. The outlet fixture bounds an exhaust opening substantially aligned with the exhaust opening of the second liner end element.
According to the principles of this invention, a method for controlling particulate generation by exhaust process gas from a substrate processing reactor includes:
directing the exhaust process gas through a liner having a plurality of surfaces wherein the liner is heated only by the exhaust process gas and deposits are formed on the heated liner; and
orienting the plurality of surfaces to dissipate backpressure created by the exhaust process gas.
In another embodiment, a method for controlling particulate generation by exhaust process gas from a substrate processing reactor includes:
passing the exhaust process gas into an inlet of an exhaust particulate controller;
passing the exhaust process gas from the inlet through a plurality of baffles
wherein each baffle includes a first surface bounding a first opening with a first dimension and a second surface bounding a second opening of a second dimension where the second dimension is smaller than the first dimension;
an inner surface of the baffle extends from a boundary of the first opening to a boundary of the second opening to define a gas flow path through the baffle; and
passing the exhaust process gas from the plurality of baffles to an outlet of the exhaust particulate controller.
Each embodiment of this invention reduces the particulate contamination in the substrate processing reactor created by process gas changes in the exhausts lines. In one embodiment, the substrate processing reactor is a barrel epitaxial reactor. Consequently, the exhaust gas particulate controller and related methods result in better substrate production than prior art systems without the controller of this invention.